Unveiling the Reaction Dynamics of Electron-Induced Chemical Reactions: A Femtosecond Time-Resolved Mass-Spectrometry Approach*

Electron-induced chemical reactions represent a fundamental yet complex phenomenon with significant implications in various fields such as astrochemistry, atmospheric chemistry, and plasma processing. When energetic electrons collide with molecules, they impart sufficient energy to induce electron loss and bond breakage, forming multiple ions. Our understanding of the mechanisms underlying the formation of tens to hundreds of ions from medium-sized molecules, as it occurs in mass spectrometry, remains limited, primarily due to challenges in tracking the reaction dynamics with femtosecond time resolution. In this presentation, we introduce a novel approach based on the strong-field electron recollision processes, recognized by the 2023 Physics Nobel Prize, to achieve time-resolved electron-induced chemical reactions. Leveraging femtosecond time-resolved electron-ionization mass spectrometry, our laboratory has investigated various molecular rearrangements, including the McLafferty rearrangement, retro-Diels Alder reaction, and neutral species roaming. Our experimental observations shed light on the ultrafast dynamics following electron-induced reactions, providing insights into high-energy chemical processes characterized by multiple ionization and fragmentation pathways. Moreover, our findings contribute to validating quantum mechanical models aimed at predicting product ion distributions, thus advancing our understanding of electron-molecule interactions and their broader implications.